Congestive Heart Failure (CHF) refers to a clinical syndrome of symptomatic events associated with compromised cardiac function. The term “heart failure” may describe the inability of the heart to supply sufficient blood flow to meet the physiological needs of the peripheral tissues. Heart failure may be associated with one or both of systolic dysfunction and diastolic dysfunction.
Systolic dysfunction refers to the inability of the cardiac contractile mechanism to develop adequate force, e.g., the inability to overcome mechanical afterload. The heart may compensate for reduced systolic function by dilating or stretching in order to improve ejection by increasing preload via the Frank-Starling mechanism. Thus, systolic dysfunction may often be characterized by a dilated, thin-walled ventricle with low ejection fraction.
Diastolic dysfunction refers to the inability of a ventricle to adequately fill. Diastolic dysfunction may arise from several mechanisms, including hypertension. Increased afterload due to increased systemic vascular resistance or reduced arterial compliance can lead to increased wall stress according to the Law of LaPlace. The ventricle may compensate for such increased wall stress by thickening or hypertrophying. Thus, diastolic ventricular dysfunction may often be characterized by ventricular hypertrophy and, perhaps, increased ejection fraction.
Hypertension may be a precursor to, or aggravating factor for, heart failure. Renal failure may occur as a result of heart failure, or may occur independently of heart failure, and may result in hypertension, edema, or peripheral fluid accumulation. A variety of cardiovascular pressures, e.g., intracardiac, arterial, and venous pressures, have been proposed as indicators of the progression of maladies such as heart failure, hypertension, or renal failure, as well as the hemodynamic status of patient in general. The progression of heart failure and renal failure may also be monitored based on thoracic or peripheral fluid accumulation, i.e., edema.